1. Field of the Invention
The present invention relates to a sheet member positioning device which positions a sheet member.
2. Description of the Related Art
Printing plate exposure devices have been developed which expose (record) an image directly by a laser beam or the like onto an image forming layer (photosensitive layer, emulsion surface) on a support of a sheet-shaped printing plate (for example, a so-called photopolymer plate or a thermal plate).
In such a printing plate exposure device, the printing plate which is loaded on a flat-plate-shaped plate is, as needed, conveyed to a punching section, and is subjected to punching processing (a processing for forming punch holes) at the punching section. Further, the printing plate, which is loaded on the plate, is conveyed to an exposure section, and exposure processing of the printing plate is carried out at the exposure section.
In order to improve the accuracy of the punching processing and the exposure processing, the printing plate must be positioned at a predetermined printing plate positioning device before the punching processing in the punching section and the exposure processing in the exposure section.
Here, if the size of the printing plate can be detected simultaneously with the positioning of the printing plate by using the printing plate positioning device, there is no need for a separate mechanism for detecting the size of the printing plate, and costs can therefore be reduced. Further, because there is no need for a separate period of time for detecting the size of the printing plate, it is possible to prevent the productivity from deteriorating.